Parascaris sp. is the largest parasitic nematode of horse causing digestive and respiratory disorders to the animal. The control of equine ascaridiosis relies on anthelmintic treatments including macrocyclic lactones (MLs) as the gold standard. However, control of infestation is increasingly difficult due to the emergence of resistant parasites throughout the world. In the free-living model nematode Caenorhabditis elegans, glutamate-dependent chloride channel receptors (GluCls) were identified as the main targets of MLs. However, in Parascaris sp, the mode of action of MLs remain poorly understood. Here we identified the Parascaris sp. GluCls and characterized the effect of a wide range of MLs. Using a candidate gene approach, we identified the orthologs of 6 genes encoding GluCls subunits in Parascaris sp. The complete cDNAs encoding these subunits were amplified by PCR and cloned into a transcription vector. The corresponding cRNAs were synthesized in vitro and then microinjected into Xenopus laevis oocytes. Two-electrode voltage-clamp experiments were performed on recombinant GluCls to investigate their pharmacological properties. Thus, the expression of a single subunit and combination of different subunits in Xenopus oocytes allowed us to obtain the functional homeric and heteromeric GluCls of Parascaris sp. The receptors were both sensitive to glutamate and ivermectin but the effect of seven different ML compounds revealed striking differences. The physiological function and the impact of MLs on these receptors in vivo are in progress. This study, provides a better understanding of the pharmacology of GluCls as well as the mode of action of MLs in nematode parasites.